Recent findings suggest that in addition to causing a number of common respiratory diseases of children, the paramyxoviruses may be involved in such diseases as multiple sclerosis and subacute sclerosing panencephalitis by means of persistent infections which involve a delicate balance between virus and host. Employing Newcastle disease virus (NDV), a model paramyxovirus, this project is concerned with the factors which control the conversion of the host cell from the production of host cell proteins to the production of virus-specific proteins and the effects which these proteins have on the infected cell. The biological effects of NDV infection can now be approached in terms of the biochemical events which cause them. In particular, we are concentrating on: 1) characterizing virus-specific messenger RNA under various conditions of infection; 2) correlating messenger activity of specific messengers with specific proteins; 3) characterizing virus-specific proteins with particular reference to control, rates of synthesis, and processing; 4) analyzing cell membrane alteration; and 5) analyzing the effects of infection on host cell protein synthesis. Techniques being used include: a) incorporation of radioactive precursors; b) cell and virus fractionation; c) fractionation of RNA and proteins by velocity sedimentation, column chromatography and acrylamide gel electrophoresis; and d) identification of virus-specific changes by immunological, biological, and biochemical procedures.